An expedient aralkylation of Baylis-Hillman adduct via the Pd-catalyzed decarboxylative protonation strategy

An expedient protocol of aralkylation of Baylis-Hillman adducts has been developed. This method used Pd-catalyzed decarboxylative protonation strategy to the allyl ester precursor that was made from the Baylis-Hillman adduct and allyl phenylacetate.     

An expedient synthesis of 2,4,5-trisubstituted 1,4-pentadienes from Baylis-Hillman adducts via the Pd-catalyzed decarboxylation-elimination protocol

We disclosed an efficient synthetic method of 2,4,5-trisubstituted 1,4-pentadienes from Baylis-Hillman adducts via the Pd-catalyzed decarboxylation-elimination protocol as the key step.     

Synthesis of poly-substituted tetrahydropyridines from Baylis-Hillman adducts modified with N-allylamino group via radical cyclization

An expedient method was developed for the synthesis of 1,4,5,6-tetrahydropyridines by radical cyclization protocol involving consecutive 1,5-hydrogen transfer and double bond isomerization process starting from Baylis-Hillman adducts.     

Synthesis of N-tosyl-3,3,4-trisubstituted pyrrolidine derivatives starting from the Baylis-Hillman adducts via radical cyclization

N-Tosyl-3,3-disubstituted-4-vinylpyrrolidine derivatives 3a-c were synthesized via radical cyclization from the modified Baylis-Hillman adducts 2. The required starting materials 2a-c were prepared in moderate yields from the Baylis-Hillman adducts in three steps: (i) acetylation of the Baylis-Hillman adducts, (ii) S_N2′ reaction with tosylamide to prepare 1, and (iii) alkylation with 1,4-dibromo-2-butene.     

Synthesis of indolequinones via a Sonogashira coupling/cyclization cascade reaction

A mild strategy for constructing indolequinone motifs is described on the basis of the Sonogashira reaction and a copper-catalyzed intramolecular cyclization cascade reaction. The first step involves the palladium- and copper-catalyzed reaction between halogenated naphthoquinone and terminal acetylene to generate a coupling product, which then reacts in a copper-catalyzed intramolecular cyclization with the nitrogen functional group adjacent to the carbon-carbon triple bond.     

Palladium-catalyzed carbonylative cyclization of Baylis-Hillman adducts. An efficient approach for the stereoselective synthesis of 3-alkenyl phthalides

A palladium-mediated carbonylative cyclization reaction of Baylis-Hillman adducts is disclosed. This simple, efficient and straightforward sequence leads to the formation of an array of 3-alkenylphthalides with different substitution patterns on the aromatic ring, with good chemical yields and selectivities.     

Palladium-catalysed intramolecular enolate O-arylation and thio-enolate S-arylation: synthesis of benzo[b]furans and benzo[b]thiophenes

Enolates derived from α-(ortho-haloaryl)-substituted ketones undergo palladium-catalysed C-O bond formation to deliver benzofuran products in good yield. A catalyst generated from Pd₂(dba)₃ and the ligand DPEphos effects the key bond formation to deliver a variety of substituted products from both cyclic and acyclic precursors. The analogous thio-ketones undergo C-S bond formation using identical reaction conditions and are converted to benzothiophene products. A cascade sequence that produces the required α-aryl ketones in situ has also been developed, although the substrate scope is more restricted.     

Synthesis of 1,5-dicarbonyl and related compounds from Baylis-Hillman adducts via Pd-mediated decarboxylative protonation protocol

We prepared various 1,5-dicarbonyl and related compounds from Baylis-Hillman adducts by using a Pd-mediated decarboxylative protonation protocol.     

Synthesis of benzofurans via Pd-catalyzed oxidative cyclization of 2-allylphenols

Substituted 2-methylbenzofurans were obtained from 2-allylphenols via Pd²⁺-catalyzed oxidative cyclization using Cu(OAc)₂–LiCl as a reoxidant and wet DMF as a solvent.     

An efficient synthesis of Baylis-Hillman adducts of acrylamide: Pd-catalyzed hydration of Baylis-Hillman adducts of acrylonitrile

An efficient palladium-catalyzed two-step protocol for the synthesis of Baylis-Hillman adducts of acrylamide was developed. The method involved the preparation of Baylis-Hillman adducts of acrylonitrile and a Pd-catalyzed hydration of nitrile with acetaldoxime.     

Synthesis of 3,4-disubstituted 2,5-dihydrofurans starting from the Baylis-Hillman adducts via consecutive radical cyclization, halolactonization, and decarboxylation strategy

A facile synthetic method of 3,4-disubstituted 2,5-dihydrofurans and 2,5-dihydropyrroles starting from the Baylis-Hillman adducts was developed. The 2,5-dihydrofuran skeleton was constructed via the consecutive radical cyclization, hydrolysis, halolactonization, and spontaneous decarboxylation strategy starting from the modified Baylis-Hillman adducts.     

Facile synthesis of benzofulvene derivatives from Baylis-Hillman adducts: In-mediated Barbier reaction combined with Pd(0)-catalyzed intramolecular Heck-elimination cascade

A facile synthesis of benzofulvene derivatives was carried out starting from the Baylis-Hillman adducts of 2-bromobenzaldehyde via the sequential bromination, In-mediated Barbier reaction with aldehyde, acetylation, Pd-catalyzed intramolecular Heck reaction, and the elimination of AcOH.     

Synthesis of 1,2,3-triazole-fused heterocycles via Pd-catalyzed cyclization of 5-iodotriazoles

A convenient approach toward polycyclic frameworks containing fused 1,2,3-triazoles is described. The synthesis consists of a Cu-catalyzed cycloaddition and an intramolecular Pd-catalyzed direct arylation or Heck reaction, and affords the products in good to excellent yields.     

Synthesis of isochromenones and oxepines via Pd-catalyzed cascade cyclization of alkynes and benzynes involving C-H activation

A new method for the synthesis of various isochromen-6-ones and phenanthro[1,10-bc]oxepines via a palladium-catalyzed cascade carbocyclization of 2-iodobenzyl-3-phenylpropiolates and 1-iodo-2-(2-(phenylethynyl)benzyloxy)benzenes with arynes is described. The reactions involve interesting biscarbocyclization of alkynes and benzynes and C-H bond activation.     

Synthesis of 3-substituted indazoles and benzoisoxazoles via Pd-catalyzed cyclization reactions: application to the synthesis of nigellicine

Syntheses of 3-substituted indazoles and benzoisoxazoles were efficiently accomplished with the aid of Pd-catalyzed intramolecular carbon-nitrogen and carbon-oxygen bond formations. The catalyst system described herein allows the cyclization to proceed under very mild conditions and thus could be applied to a wide range of substrates with acid- or base-sensitive functional groups. A total synthesis for the indazole ring-containing natural product nigellicine is also described.     

Palladium-catalyzed synthesis of indane and cyclobuta[a]indenes from homoallylic alcohols derived from Baylis-Hillman adducts: base-dependent stereoselectivity for the benzylidene group in cyclobuta[a]indene

Various indane and cyclobuta[a]indene derivatives were synthesized by palladium-catalyzed cyclization of homoallylic alcohol derivatives prepared from Baylis-Hillman adducts. Especially, cyclobuta[a]indene derivative was synthesized stereoselectively by palladium-catalyzed 5-exo-trig/4-exo-trig cascade cyclization, albeit in moderate yield. The Z isomer was formed exclusively in the presence of Et₃N by usual Heck-type carbopalladation process while E isomer with Cs₂CO₃ most likely by a concerted metalation/deprotonation (CMD) process.     

Synthesis of sterically congested bicyclic tetrahydrofurans via Pd-catalyzed cyclization

Prins-type cyclization followed by palladium-catalyzed cyclization provided sterically congested bi- or tricyclic tetrahydrofurans, which are very stereoselective as well. cis-2,5-Disubstituted tetrahydrofurans obtained from Prins-type cyclization have an allenyl group and a functional group such as alcohol, carboxylic acid, and aryl halide. The tetrahydrofurans bearing an allene group underwent palladium-catalyzed cyclization to give sterically congested bi- or tricyclic tetrahydrofurans.     

Studies on montmorillonite K10-microwave assisted isomerisation of Baylis-Hillman adduct. Synthesis of E-trisubstituted alkenes and synthetic application to lignan core structures by vinyl radical cyclization

The isomerisation of acetates from the Baylis-Hillman adducts with Mont.K10 clay-microwave combination furnished E-trisubstituted alkenes in high yield. The simple Baylis-Hillman adducts with trimethyl orthoformate and unsaturated alcohols under clay catalytic condition gave densely functionalised-isomerized products under solvent free condition. Application of the propargyl derivatives thus obtained from the isomerisation of the Baylis-Hillman adducts with propargyl alcohol has been demonstrated in the synthesis of lignan core structures by tri-n-butyltin hydride mediated vinyl radical cyclization.     

Synthesis of poly-substituted nitrobenzene derivatives from Baylis-Hillman adducts via [3+3] annulation protocol

Poly-substituted nitrobenzenes were synthesized from Baylis-Hillman adducts via the [3+3] annulation strategy as the key step. 1,3-Dinitroalkanes served as the 1,3-dinucleophilic component and the Baylis-Hillman acetates as a 1,3-dielectrophilic part.